Date of Award

5-15-2022

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Derek P. Crane

Second Advisor

Erin J. Burge

Third Advisor

Kyle Hartman

Additional Advisors

Christopher E. Hill; Scott Smith

Abstract

Catch-and-release (C&R) has become a popular practice in many fisheries, both as a management strategy and as an angler ethic. The practice has been used to both increase the abundance and size structure of fish populations but relies heavily on the assumption that released fish survive the encounter. The Muskellunge (Esox masquinongy) is a large-bodied, coolwater predatory game fish that is highly prized by many anglers. Many Muskellunge fisheries have transitioned to almost exclusively C&R angling. Muskellunge fisheries have increased in both number and popularity, particularly in southern and mid-Atlantic rivers. However, there is little information on population characteristics for these fisheries, thus, limiting biologists’ ability to effectively manage them. The James River, Virginia supports a popular Muskellunge fishery, but information on Muskellunge abundance and angler use of the resource were unknown. Therefore, I utilized data from simultaneously conducted fishery dependent tag-return and fishery independent capture-recapture studies to estimate C&R exploitation and abundance of Muskellunge in the James River 141 km upstream of Lynchburg, VA. Winter electrofishing surveys were conducted by the Virginia Department of Wildlife Resources (VDWR) in 2016–2019, during which they tagged 747 individual Muskellunge with dart tags and passive integrated transponders. Using angler tag-return data and a Brownie dead-recovery model, I observed that C&R exploitation (u) differed between the upper (u = 0.57 ± 0.09) more free flowing reach and lower (u = 1.00 ± 0.10) more impounded reach of the study area. I then used capture-recapture data from VDWR electrofishing surveys in a Jolly-Seber open population model to estimate densities of adult (≥762 mm) Muskellunge. Similarly, densities differed between the two reaches (upriver = 0.80/ha, downriver = 0.50/ha), but were comparable to densities observed in lakes and at least one other river throughout the Muskellunge’s distribution. Given the high rates of C&R exploitation in the James River and growing popularity of Muskellunge angling in southern waters, investigations into the effects of this level of angling on the James River Muskellunge population are necessary. Because Muskellunge are a coolwater species, populations in the southern portion of their distribution are more likely to experience temperatures above their thermal optima, especially in the summer. Therefore, anglers on the James River have expressed concerns regarding the population-level effects of additional mortality from C&R during periods of elevated water temperatures. To address these concerns, I used a combination of a radio telemetry study and individual growth model simulations to evaluate the effects of warm-water C&R mortality on the length potential of the James River Muskellunge fishery. I implanted radio transmitting tags in fishable (≥650 mm) Muskellunge in winter 2020 (N = 45) and 2021 (N = 50) to monitor fates of fish that were subsequently caught and released during the warm-water period (July – August). Twelve tagged fish were caught and released in the warm-water period, of which four died (33%). Despite a high mortality rate compared to studies conducted during cooler temperatures, our simulations indicated that a closed season during the warm-water period on the James River would result in little to no increase in the proportions of Muskellunge reaching preferred (1020 mm) and memorable (1140 mm) size classes. The small observed differences in the change in these proportions of large size classes, including in scenarios allowing fish to achieve larger ultimate lengths in the simulations, are because (1) thermally stressed fish were not susceptible to angling, and (2) growth potential beyond the memorable size class is limited for the James River based on my length-at-age data. Results from this study will provide managers with the information necessary for developing more comprehensive Muskellunge management plans, including other systems in the Muskellunge’s southern distribution.

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